Gas generator



M. CRANE Dec. 2, 1969 GAS GENERATOR 2 Sheets-Sheet J.

Filed May 9, 1968 INVENTOR. Michae/ rcm e,

% y f-?TTORNEY M. CRANE Dec. 2, 1969 GAS GENERATOR 2 Sheets--Sheet 2 Filed May 9 1968 I INVENTOR. M chae/ rane 97 TOPNEY 3,481,149 GAS GENERATOR Michael Crane, West Orange, NJ., assignor to General Pneumatics Corporation, Newark, NJ., a corporaton of New Jersey Filed May 9, 1968, Ser. No. 728,003

Int. Cl. F17b 7/02 U.S. Cl. 62-45 8 Clams ABSTRACT OF THE DISCLOSURE Apparatus for evaporating a lquified gas wherein the heat of vaporization is supplied by means of initiating a chemical reaction in proximity to the liquid and the gas is ported from the apparatus via a tubular heat exchanger, the heat exchanger being in contact with the region in which the chemical reaction occurs. The apparatus also comprises pressure sensitive valve means for selectively releasing the products of the Chemical reaction into the reservoir for the lquified gas to maintain pressure therein.

BACKGROUND OF THE INVENTION Field of the invention Gas generators wherein a lquified gas, usually carbon dioxde, is evaporated to provide a pressurized gas `are well known in the art. The heat for vaporization of the lquified gas has typically been provided by the combustion of a charge of material located in proximity to the reservoir for the lquified gas. The thus generated gas would thereafter be released to the desired environment via a port which was usually opened simultaneously with the ignition of the charge.

Gas generators of the type described above, particularly those which are portable in nature, have found wide utility. Examples of such utility may be found in flota tion equipment, such as life rafts or jackets, and safety and convenience equipment, such as inflatable pads or matt'esses. However, despite their wide usage, the prior art gas generators have had certain inherent deficiences.

One of the major problems with prior art gas generators has been overcooling of the discharge passage for the generated gas. Where the gas is carbon dioxide, it is not uncommon to have restricton of the exit passage through the formation of solid carbon dioxide.

Another problem inherent in the prior art resides in the maintenance of pressure within the reservoir as the evaporation process continues. Prior art gas generators have not provided for -self-regulation of output pressure which, for many uses is desirable.

SUMMARY OF THE INVENTION The present invention overcomes the foregoing and other -disadvantages of the prior art by providing a novel method for the evaporation of a lquified gas and `apparatus embodying that method. The 'apparatus comprises 'a reservoir for the lquified gas and, disposed therein, a reaction chamber wherein a pair of reactable materials are stored in spaced apart relationship. A Chemical reaction between these materials is initiated by melting a separating -Unted States Patent O 3,48l,l49 Patented Dec. 2, 1969 barrer, the melting preferably being accomplished by electrio heating, and the thus initiated Chemical reaction produces heat for the vaporization of the lquified gas. The generated gas is discharged from the reservoir through a heat exchange tube which passes through the reaction chamber whereby heat is applied in the region where the gas exits from the apparatus.

In accordance with the present invention, the reaction chamber may be placed into communication with the interior of the reservoir by means of a pressure sensitive valve which operates in response to the pressure difierential between the reaction chamber and reservoir. Accordingly, when the pressure within the reservoir drops below a predetermined level, gaseous reaction products will be released from the reaction chamber into the reservoir thereby providing a degree of self-regulation of the apparatus output pressure.

Communication between the interior of the apparatus of the present invention and the utilization device, when use of the apparatus is desired, is achieved by means of puncturing a ru-pture disc which normally closes the exit ,port of the apparatus. Fracturng of this rupture disc, in a preferred embodiment, is accomplished by means of a solenoid operated plunger.

BRIEEDESCRIPTION 'OF THE DRAWING The present invention may be better understood and its numerous advantages will become apparent to those skilled in the art by reference to the accomp'anying drawing wherein like reference numerals refer to like elements in the various figures and in which:

FIGURE 1 is a cross-sectional view of a preferred embodiment of the present invention;

FIGURE 2 is a partial, cross-sectiona-l -view, taken along line 2-2 of FIGURE 1, of the reaction chamber of the preferred embodiment of the present invention;

FIGURE 3 is an enlarged, cross-sectional view of 'an end of the reaction chamber portion of the preferred embodiment of the present invention, FIGURE 3 depicting the pressure regulating valve of the present invention.

FIGURE 4 is a partial cross-sectional View of an embodiment of the present invention employing a solenoid operated rupture disc fracturing means.

prises a bottle or reservoir 10 which is charged with a lquified gas 12, the gas typically being carbon dioxide.

In order to withstand the pressures and temperatures to i which it will be subjected, and also to provide a safety factor which will prevent 'any undesired release of the lquified gas, bottle 10 will be formed of a metallic material and will, at its discharge end or neck 14, be internally threaded so that it may be mated with a nipple, such as shown at 16, on an inflatible or other gas utilization devce.

A cylindrically shaped device, indicated generally at 18, will be Suspended within reservoir 10. The disposition of the member 18 within the reservoir is accomplished by means of its having 'an externally threaded first or discharge end 20 which mates with the internally threaded neck 14 of the reservoir. Member 18 comprises a reaction chamber 22, a heat exchanger tube 24 through which the gas will be discharged from the reservoir and a -pressure sensitive check valve device 26. The check valve 26 operates in the manner to be described below and may be of the leaf spring type. The reaction chamber 22 is defined by the inner wall of a cylindrical outer member 27 and the outer wall of heat exchanger tube 24 and the reaction chamber extends between a first spacer-retaining member 28 located adjacent the discharge end of the heat exchanger tube and a second or Upstream spacer-retaining membr 30 located adjacent the entrance end of the heat exchanger tube. Positioned within reaction chamber 22 will be chemicals which, when brought into contact, will spontaneously react chemically, and exothermic reaction being desired. Such a reaction may *be achieved by reacting an acid with a carbonate, a hypochlorite with a carbamate or by the hydration *of an anhydride. In FIGURE 1, the chemicals are indicated by a solid chemical cartridge 32 and a liquid Cartridge 34. Liquid chemical Cartridge 34 will butt, at one end, against spacer :ring 30, the other end of the liquid chemical cartridge being separated from the solid chemical cartridge by means of a Cartridge seam melter 36 In a preferred embodiment, the seam melter 36 may comprise electrical contacts which, in combination with a metallized strip on the seam of the plastic cartridge 34, forms an electric heater. The end of the solid chemical Cartridge 32 disposed opposite to the Cartridge seam melter 36 will butt against a perforated spacer ring 38 which may be integral with the first spacer ring 28.

As may best *be seen from a simultaneous consideration of FIGURES 1 and 2, a plurality of gas tubes 40-40 provide communication between the region between spacer ring 28 and perforated spacer 38 and the region between spacer ring 30 and the regulating valve means 26. Spacer ring 28 is sealed about the periphery `of the heat exchanger tube 24 while spacer ring 30 is sealed about the heat exchange tube and the gas tubes 40. Accordingly, through the action of gas tubes 40 and the perforated spacer ring 38, the interior of reaction chamber 22 is in communication with a first side of the valve means 26. The opposite side of the valve means 26 is in `direct communication with the interior reservoir Via apertured retaining member 42 which threadably engages the cylindrical member 27 adjacent its inwardly disposed end.

As may also be seen from FIGURE 2, the heat ex- Changer tube 24 is provided -with internal fin members 44. As will become more apparent from the discussion below of the operation of the disclosed embodiment, presence of the fin members aids in the transfer of heat to the gas being discharged from the apparatus, the fins being heated by conduction from the wall of the heat exchanger tube 24 which defines the inner wall of the reaction chamber.

Prior to utilization of the gas generator of the present invention, leakage of the contents of reservoir 10 is prevented by means of a rupture disc 46 which bridges the neck 14 of reservoir 10. Rupture disc 46 is held in position 'between a retaining nut 48 and the downstream or discharge end of member 18. -Rupture disc 46 may be fractured manually with a suitable tool, the rupture disc may be pressure sensitive and thus will fracture when the pressure within reservoir 10 reaches a predetermined level or the rupture disc may be shattered by means of the apparatus of FIGURE 4. In FIGURE 4, the rupture disc is punctured by a pointed extension 50 of a plunger 52. Plunger 52 is normally spring loaded via spring 54 in a direction away from the rupture disc. However, upon energization of a solenoid 56, the plunger will be urged forward compressing spring 54 and pointed extension 50 -will puncture the rupture disc thus releasing the contents of reservoir 10. The gas escaping from the reservoir will be directed outwardly through oppositely disposed discharge ports 58 and 60 in the solenoid housing 62. It is also to be noted that the rupture disc 46 forms a part of the solenoid assembly in the embodiment of FIGURE 4 and, of course, the device may be reused by removing apertured retaining nut 48 and inserting a new rupture disc.

In the preferred embodiment of the present invention, as noted above, the Cartridge seam melter 36 is an electrical heating element. Current is supplied to seam melter 36 via conductors 70 which communicate between the ex terior and interior of the apparatus. Conductors 70 pass through the wall of reservoir 10, preferably in the vicinity of the neck portion 14 as shown, and thereafter pass into the interior of the reaction chamber through the walls of cylindrical member 27. Sealing means, not shown, are provided to prevent leakage between the interior and exterior of reservoir 10 around conductors 70. In the reaction chamber 22, the conductors are positioned along one of gas tubes 40.

In operation, the device 18 is loaded by the insertion in 'reaction chamber 22, of the solid chemical Cartridge 32 and the liquid chemical cartridge 34. The solid chemical will typically be in granular form and the cartridge therefore will be a perforated basket or woven wire cage. The liquid chemical Cartridge will be an annular shaped plastic bag. In loading member 18, chemical cartridges 32 and 34 will be inserted serially. After loading, the spacer ring or rings and retaining nuts will be threadably engaged -with member 27 thus completing the assembly of the exothermic chemical Ieactor and heat exchanger.

Once device 18 has been loaded, it *will be inserted into reservoir 10. The discharge end 20 of device 18 will threadably engage the internally threaded neck 14 of reservoir 10 thus looking the device 18 into position. Reservoir 10 is then suitably charged with a liquified gas in a manner well known in the art. Thereafter, the rupture disc 46 will be positioned so as to seal off the interior of the apparatus and the retaining nut -48 will be inserted to complete the assembly.

When it is desired to employ the present invention, current will be supplied to seam melter 36 via conductors 70. The passage of current through the metallized strip which is in contact with the bottom seam of the plastic liquid Cartridge 34 melts the plastic allowing the chemicals of the liquid and solid cartridges to contact each other thereby starting an exothermic chemical reaction. Restated, the melting of the seam on the liquid Cartridge 34 results in the liquid pouring out of its container or in the solid chemical cartridge falling into the now open liquid Cartridge. The attitude or orientation of the apparatus at the time of actuation 'will determine -which occurs.

Independently, at this time, the rupture disc 46 will be punctured either manually or by energization of solenoid 56 of the embodiment of FIGURE 4. The chemical reaction which takes place in reaction chamber 22 furnishes the heat required to vaporize the liquified gas which flows through the heat eXc-hanger tube 24 upon the breaking of the rupture disc 46. Restated, the chemical reaction in reaction chamber 22 results in the heating of the walls and fins of the heat exchanger tube 24 and thus results in the vaporizing of material escaping from the reservoir 10 through the heat exchanger tube. Heat is thus applied in the region where the gas exists from the reservoir by reacting the heat producing chemicals in an annular chamber which surrounds the exit passage. The heat demand is maximized in the discharge passage by restricting the latter so that a significant portion of the total pressure differential between the reservoir and utilization device is incurred where the material passes from the interior to exterior of the apparatus.

As the reaction proceeds, gaseous reaction products are generated within reaction chamber 22 thereby developing a positive pressure within the reaction chamber. As the liquified gas 12 flashes into vapor and discharges from the apparatus, the pressure within reservoir 10 decreases. When the pressure differential across valve means 26 becomes great enough, the valve opens, as shown in FIG- URE 3, and the gaseous reaction products enter the reservoir where they mix with the remaining charge material. Thus, use of a chemical reaction where the reaction products are gases, in combination with the pressure sensitive valve means, provides a degree of self-regulation in the present invention.

It should also be noted that the problems of the prior art which resulted from overcooling in the discharge path are overcome by the present invention. Further, any cooling which does occur in the discharge passage results in a self-compensating action through the efiicient heat exchange of the present invention. That is, overcooling of the discharge passage will result in a lower temperature in the reaction chamber thereby reducing the reaction chamber pressure and consequently speeding up the exothermic chemical reaction.

A heat insulato- 47 retards conduction of heat from the seam melter 36 to the liquid in the cartrdge, thereby concentrating the heat on the cartridge seam.

While a preferred embodiment has been shown and described, various modifications and substit-tions may be made thereto without departing from the spirit and scope of the present invention. Accordingly, it is to be understood that the present invention has been disclosed by way of illustration and not limitation.

I claim:

1. A gas generator comprising a reservoir for an inert liquid to be vaporized into gaseous form, said reservoir having a gas discharge port therein;

a reaction chamber disposed within said reservoir;

means for initiating a chemical reaction within said reaction chamber to thereby generate heat within said reservoir to vaporize said liquid, and

tubular surface heat exchanger means extending through said reaction chamber and communicating at its ends, respectvely, with said gas discharge port and the interior of said reservoir, whereby heat generated in said reaction chamber by said chemical reaction will be transferred to fluid passing through said heat exchanger means.

2. The gas generator of claim 1 wheren said reservoir, reaction chamber and heat exchanger are coaxal, said gas discharge port is at one end of said reservoir and the ends of said reaction chamber are disposed, respectively, adjacent said gas discharge port and between the ends of said reservoir.

3. The gas generator of claim 2 with the addition of pressure sensitive valve means communicating between the nterior of said reaction chamber and the interior of said reservoir, said valve means Operating to permit mixing of reaction products with the contents of the reservoir.

6 4. The gas generator of claim 1 wherein said means for initiating a chemical reaction comprises:

a first Cartridge containing a first chemical in liquid form; a second chemical, said first and second chemicals reacting exothermically when mixed, and electric heater means for rupturing said first Cartridge. 5. The gas generator of claim 2 wheren said means for initiating a chemical reaction comprises:

a first plastic cartridge containing a first chemical in liquid form; a second chemical, said first and second chemicals reacting exothermically when mixed, and electric heater means for melting a portion of said first cartrdge to thereby allow mixing of said chemicals. 6. The gas generator of claim 5 further comprising: pressure sensitive valve means communicating between the interier of said reaction chamber and the reservoir, said valve means Operating to permit mixing of products of said exothermic chemical reaction with the contents of the reservoir to maintain reservoir pressure. 7. The gas generator of claim 6 further comprising: rupture disc means for sealing said gas discharge port prior to use of the apparatus. 8. The gas generator of claim 7 wheren said rupture disc means comprises:

a rupture disc; pointed rod means for rupturing said disc, and solenoid means for urgng said rod into contact with said disc upon energization.

References Cited UNITED STATES PATENTS 2,671,312 3/1954 Roy -251 3,143,446 8/ 1964 Berman 60-251 3,182,445 5/1965 Lowes 60-251 3,353,358 11/ 1967 Lovingham 62-39.48

LLOYD L. KING, Primary Examner U.S. Cl. X.R. 60-39.48; 62-52 

